Laminate, element comprising said laminate, and method for manufacturing said laminate

Abstract

The invention provides a laminated body, an element comprising the laminated body, and a method for manufacturing the laminated body. The laminate has: a piezoelectric layer formed from a crystal of an oxide having piezoelectric properties; a metal layer; and a magnetic material layer formed of a crystal of a Heusler alloy as a ferromagnet, in which the piezoelectric material layer, the metal layer, and the magnetic material layer are laminated in this order.

Description

Technical Field

[0001] The present invention relates to a laminate, a device including the laminate, and a method for producing the laminate. Background Art

[0002] For example, as disclosed in Patent Document 1, it is known that when vibrations such as acoustic waves are injected into a magnet, spin waves (sometimes also referred to as spin currents or magnons) are generated in the magnet. Components utilizing such generated spin waves are also known.

[0003] Patent Document 1 discloses an acoustic wave-spin current conversion element. The element comprises: an acoustic wave generating member; a magnetic member that generates a spin current using an acoustic wave from the acoustic wave generating member; an inverse spin Hall effect member that is injected with the spin current generated by the magnetic member; and a magnetic field applying unit that limits the magnetization direction of the magnetic member. In this element, an acoustic wave-induced spin current is extracted from the inverse spin Hall effect member. Specifically, a spin current is generated by an acoustic wave perpendicularly incident on the magnetic member, thereby pumping the spin current in a perpendicular direction from the interface to the inverse spin Hall effect member. In addition, Patent Document 1 discloses that when an acoustic wave is injected into the magnetic member, an acoustic wave-induced spin current is generated in the magnetic member.

[0004] Patent Document 2 discloses a magnetic thin film and a magnetoresistive effect element and a magnetic device using the same. The magnetic thin film has a substrate and Co2Fe(Si) 1-x Al x ) film, Co2Fe(Si 1-x Al x ) film has an L21 or B2 structure, and 0<x<1. Tunneling magnetoresistance (TMR) effect elements and giant magnetoresistance (GMR) effect elements using this magnetic film can obtain large TMR and GMR at room temperature under low current and low magnetic field conditions. In this magnetic film, it is also possible to 1-x Al x ) films. The buffer layer may be at least one of Cr, Ta, V, Nb, Ru, Fe, FeCo alloy, and full Heusler alloy.

[0005] Non-Patent Document 1 discloses the following: various buffer layers (such as Mo and Ti) are deposited on a lithium niobate (LiNbO3) substrate serving as a piezoelectric material, and then TbFe2, a ferromagnetic strictive material, is epitaxially grown on the buffer layer. The LiNbO3 substrate is cleaned and vacuum-treated at 500°C before use. It is disclosed that when Ti is used as the buffer layer, the Ti layer is formed at 100°C. Furthermore, it is disclosed that when Mo is used as the buffer layer, the Mo layer is formed at 450°C. The TbFe2 layer is formed on the buffer layer at 650°C.

[0006] Non-patent document 2 discloses an example of utilizing the in-plane uniaxial magnetic anisotropy of a polycrystalline Co2FeSi film as a Heusler alloy grown on a single-crystal PMN-PT (011) substrate to perform nonvolatile and reproducible magnetization vector switching in a remanent state. 1 / 3 Nb 2 / 3 )O3-PbTiO3. The document discloses the growth of a Co2FeSi film to a thickness of 30 nm by molecular beam epitaxy (MBE). It discloses the placement of a 0.3 nm thick Fe layer between the Co2FeSi film and the PMN-PT substrate. Furthermore, regarding the Fe layer, the placement of a 0.3 nm thick Fe layer is essential for improving the crystallinity of the Co2FeSi film and the crystallinity of the L21 structured Co2FeSi film. In contrast, it is shown that a polycrystalline Co2FeSi film grown directly on a PMN-PT substrate without the use of an Fe layer is completely non-oriented. It discloses the formation of the Co2FeSi film and the Fe layer at a growth temperature of 300°C. Observation using a high-resolution transmission electron microscope revealed the formation of an amorphous layer between the PMN-PT substrate and the Co2FeSi film. Furthermore, observation using EDX spectroscopy revealed that the amorphous layer is an oxide containing almost no Co, Fe, or Si. Furthermore, the EDX spectrum is not shown in Non-Patent Document 2.

[0007] Non-Patent Document 3 discloses an example in which a sample of a thin Fe film deposited on a LiNbO3 substrate (a ferroelectric) by vapor phase epitaxy was annealed. The study investigated how the surface structure and magnetic properties of the Fe film changed with the annealing temperature. Non-Patent Document 3 shows that increasing the annealing temperature disrupts the interface structure between the Fe film and the lithium niobate substrate.

[0008] Non-Patent Document 4 discloses a method for measuring the damping constant.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: International Publication No. 2012 / 121230;

[0012] Patent Document 2: International Publication No. 2007 / 126071.

[0013] Non-patent literature

[0014] Non-patent literature 1: Epitaxial growth of TbFe2 on piezoelectric LiNbO3 Z-cut, Vincent Polewczyk et al., 2020 J. Phys.: Condens. Matter 32 235803;

[0015] Non-patent literature 2: Giant converse magnetoelectric effect in a multiferroicheterostructure with polycrystalline Co2FeSi, NPG Asia Materials. 43. ISSN 1884-4049;

[0016] Non-patent document 3: Thermal assisted tailoring of magnetic coercivity in Ironthin films on unstable Lithium Niobate substrate, Journal of Magnetism and Magnetic Materials, Volume 515, 1December 2020, 167257;

[0017] Non-patent literature 4: Temperature dependence of the effective Gilbert damping constant of FeRh thin films, T. Usami et al., AIP Advances 11, 045302 (2021). Summary of the Invention

[0018] Problems to be solved by the invention

[0019] It can be considered that in a laminate or laminated structure in which a layer of a magnetic body (hereinafter referred to as a magnetic layer) is formed on a layer of a component that generates vibrations such as a piezoelectric body (hereinafter referred to as a piezoelectric layer), if, for example, vibrations can be efficiently injected into the magnet, a spin current can be efficiently generated by the magnet. However, in the case of forming such a laminate, sometimes due to, for example, the influence of heat, the diffusion of elements in each layer, etc., the interface between these layers is disordered, and the vibration cannot be efficiently transmitted from the piezoelectric layer to the magnetic layer. Sometimes, for example, there is a situation as follows: between the piezoelectric layer and the magnetic layer, a diffusion layer is formed between the layers, in which the elements of any layer diffuse to the other layer, or a so-called irregular layer with an irregular structure, so that the vibration cannot be efficiently transmitted from the piezoelectric layer to the magnetic layer. Therefore, it is desirable to suppress the disorder of the interface between the piezoelectric layer and the magnetic layer.

[0020] Furthermore, when the interface is disturbed, the spin current in the magnetic layer may be easily attenuated. In particular, in devices utilizing spin currents, efficient generation of spin currents and suppression of spin current attenuation are desired.

[0021] The present invention has been made in view of this actual situation, and an object thereof is to provide a stacked body in which disturbance of the interface between a piezoelectric layer and a magnetic layer is suppressed, an element including the stacked body, and a method for manufacturing the stacked body.

[0022] Solutions for solving problems

[0023] The stacked body of the present invention for achieving the above-mentioned purpose comprises: a piezoelectric layer formed by crystals of an oxide having piezoelectricity; a metal layer; and a magnetic layer formed by crystals of a Heusler alloy which is a ferromagnetic body, wherein the piezoelectric layer, the metal layer, and the magnetic layer are stacked in sequence.

[0024] The element of the present invention for achieving the above-mentioned purpose comprises: a piezoelectric layer formed by crystals of an oxide having piezoelectricity; a metal layer; and a magnetic layer formed by crystals of a Heusler alloy which is a ferromagnetic body, wherein the piezoelectric layer, the metal layer, and the magnetic layer are stacked in sequence, the thickness of the metal layer is greater than 10 nm and less than 40 nm, the average oxygen content is less than 5 at %, and the average content of the metal elements constituting the metal layer within a range of 10 nm from the interface between the piezoelectric layer and the metal layer is less than 5 at %.

[0025] The manufacturing method of the stacked body of the present invention for achieving the above-mentioned purpose includes: a metal layer forming step, forming a metal layer on a piezoelectric layer formed by crystals of an oxide having piezoelectricity; and a magnetic layer forming step, forming a magnetic layer formed by crystals of a Heusler alloy which is a ferromagnetic body on the above-mentioned metal layer, in which the above-mentioned magnetic layer forming step is formed by molecular beam epitaxy at a growth temperature of not less than 80°C and not more than 450°C.

[0026] Effects of the Invention

[0027] According to the present invention, it is possible to provide a laminate in which disturbance at the interface between a piezoelectric layer and a magnetic layer is suppressed, an element including the laminate, and a method for producing the laminate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram showing the structure of the laminated body according to the present embodiment when viewed from the side.

[0029] Figure 2 It is a schematic diagram showing the structure of the element of this embodiment when viewed from the side.

[0030] Figure 3 It is a schematic diagram showing the structure of the element of this embodiment when viewed from the top surface.

[0031] Figure 4 This is an explanatory diagram of the metal layer forming process.

[0032] Figure 5 This is a diagram illustrating the etching process.

[0033] Figure 6 This is a diagram illustrating the insulating layer forming process.

[0034] Figure 7 This is a TEM image of a cross section of the laminate of Example 1.

[0035] Figure 8 This is a TEM image of the region subjected to surface analysis using EDX in Example 1.

[0036] Figure 9 This is a graph showing the concentration distribution of Nb in the laminate of Example 1.

[0037] Figure 10 This is a graph showing the concentration distribution of Cr in the laminate of Example 1.

[0038] Figure 11 Graph showing the Si concentration distribution in the laminate of Example 1.

[0039] Figure 12 This is a graph showing the Fe concentration distribution in the laminate of Example 1.

[0040] Figure 13 Graph showing the concentration distribution of Co in the laminate of Example 1.

[0041] Figure 14 It is a figure which shows the position and scanning direction of the laminated body of Example 1 by line analysis using EDX.

[0042] Figure 15 This is a graph showing the relationship between the element concentration and the scanning distance of the laminate of Example 1 by EDX line analysis.

[0043] Figure 16 This is a TEM image of a cross section of the laminate of Comparative Example 1.

[0044] Figure 17 This is a TEM image of a region subjected to surface analysis using EDX in Comparative Example 1.

[0045] Figure 18 This is a graph showing the concentration distribution of Nb in the laminate of Comparative Example 1.

[0046] Figure 19 This is a graph showing the concentration distribution of V in the laminate of Comparative Example 1.

[0047] Figure 20 This is a graph showing the concentration distribution of Si in the laminate of Comparative Example 1.

[0048] Figure 21 This is a graph showing the Fe concentration distribution in the laminate of Comparative Example 1.

[0049] Figure 22 Graph showing the concentration distribution of Co in the laminate of Comparative Example 1.

[0050] Figure 23 It is a figure which shows the position and scanning direction of the laminated body of Comparative Example 1 by line analysis using EDX.

[0051] Figure 24 This is a graph showing the relationship between the element concentration and the scanning distance of the laminate of Comparative Example 1 by EDX line analysis.

[0052] Figure 25 This is an explanatory diagram of the structure of the element used in Example 2.

[0053] Figure 26 This is a graph showing the damping constant measured in Example 2 versus the electric field strength. DETAILED DESCRIPTION

[0054] A laminate, an element, and a method for manufacturing the laminate according to embodiments of the present invention will be described with reference to the drawings.

[0055] exist Figure 1Schematic diagram of the structure of the laminated body 100 of this embodiment is shown in FIG.

[0056] The laminate 100 includes a piezoelectric layer 1 formed of a crystal of a piezoelectric oxide, a metal layer 2, and a magnetic layer 3 formed of a crystal of a Heusler alloy, which is a ferromagnetic material. In the laminate 100, the piezoelectric layer 1, the metal layer 2, and the magnetic layer 3 are stacked in this order.

[0057] As an example, the stacked body 100 can be manufactured by the following manufacturing method, which includes: a metal layer forming process, forming a metal layer 2 on the piezoelectric layer 1; and a magnetic layer forming process, forming a magnetic layer 3 formed by crystals of a Heusler alloy which is a ferromagnet on the metal layer 2, in which the magnetic layer 3 is formed by molecular beam epitaxy at a growth temperature of greater than 80°C and less than 450°C.

[0058] This laminate 100 suppresses disturbances in the interface between the piezoelectric layer 1 and the magnetic layer 3 .

[0059] The laminate 100 can be formed into a predetermined structure by etching or the like, and an electrode layer 61 or the like can be formed, thereby serving as an element 200 having a function such as a transistor.

[0060] Hereinafter, the laminated body 100 and the element 200 according to the present embodiment and their manufacturing methods will be described in detail.

[0061] As described above, the laminate 100 is a structure having a laminate structure in which the piezoelectric layer 1, the metal layer 2, and the magnetic layer 3 are laminated in this order. Figure 1 , a schematic diagram of the structure of the stacked body 100 is shown, as viewed from a direction intersecting the direction in which the layers of the stacked body 100 are stacked (i.e., from the side). In the stacked body 100, vibrations generated by applying a voltage (electric field) to the piezoelectric layer 1 can propagate from the piezoelectric layer 1 to the magnetic layer 3, thereby generating spin waves in the magnetic layer 3.

[0062] The piezoelectric layer 1 serves as a substrate for forming the metal layer 2 and the magnetic layer 3. Furthermore, the piezoelectric layer 1 serves as a vibration generator for generating vibrations injected into the magnetic layer 3, specifically, a vibration generator for generating surface elastic waves. The thickness of the piezoelectric layer 1 is, for example, not less than 200 nm and not more than 500 μm.

[0063] The piezoelectric layer 1 is formed of a crystal of an oxide having piezoelectricity and can vibrate when a voltage is applied.

[0064] The piezoelectric layer 1 is preferably single crystal. When the piezoelectric layer 1 is single crystal, the crystal order of the metal layer 2 and magnetic layer 3 formed on the piezoelectric layer 1 is improved. Furthermore, when the piezoelectric layer 1 is single crystal, the metal layer 2 and magnetic layer 3 can be grown as single crystals. This allows vibrations to be efficiently propagated from the piezoelectric layer 1 to the magnetic layer 3 via the metal layer 2, efficiently generating spin waves in the magnetic layer 3. Furthermore, the attenuation of spin waves in the magnetic layer 3 can be suppressed.

[0065] The oxide forming the piezoelectric body 1 is preferably, for example, a dielectric.

[0066] The mechanical quality factor of the oxide forming the piezoelectric layer 1 is preferably 100 or greater, more preferably 1000 or greater. The mechanical quality factor is a constant that indicates the sharpness of mechanical vibration near the resonant frequency; a larger value indicates a sharper vibration. A higher mechanical quality factor of the oxide forming the piezoelectric layer 1 allows for more efficient propagation of vibration from the piezoelectric layer 1 through the metal layer 2 to the magnetic layer 3, and more efficiently generates spin waves in the magnetic layer 3.

[0067] From the viewpoint of composition, an example of an oxide preferred as the piezoelectric layer 1 is preferably a compound represented by the chemical formula ABO3. That is, the piezoelectric layer 1 may contain a compound that can be represented by the chemical formula ABO3 as an oxide, and furthermore, the piezoelectric layer 1 may be formed of a compound that can be represented by the chemical formula ABO3 as an oxide. Here, in the chemical formula ABO3, A is a metal element, and B is one or more metal elements different from A. In addition, in the oxide represented by the chemical formula ABO3, B includes B' and B" (wherein B" is a metal element different from B'), and includes compounds that can be represented by AB'. x B″ 1-x O3 (wherein 0<x<1) compound.

[0068] Examples of preferred oxides for the piezoelectric layer 1 include silicon dioxide (quartz crystal, SiO2), lithium niobate (LiNbO3), and lithium tantalate (LiTaO3). That is, the piezoelectric layer 1 may include one or more oxides selected from silicon dioxide, lithium niobate, and lithium tantalate. Particularly preferred oxides for the piezoelectric layer 1 are oxides having an ilmenite structure, such as lithium niobate and lithium tantalate, and having a composition corresponding to the chemical formula ABO3. Furthermore, when a lithium niobate substrate is used as the piezoelectric layer 1, the lithium niobate substrate may be a Z-cut or a Y-cut.

[0069] In the piezoelectric layer 1, the average content of the metal elements constituting the metal layer 2 is preferably 5 at% (atomic percentage) or less within a 10 nm range from the interface between the piezoelectric layer 1 and the metal layer 2. This can suppress disturbances at the interface between the piezoelectric layer 1 and the metal layer 2, resulting in a smoother interface. By suppressing disturbances at the interface between the piezoelectric layer 1 and the metal layer 2, vibrations can be efficiently propagated from the piezoelectric layer 1 through the metal layer 2 to the magnetic layer 3, effectively generating spin waves in the magnetic layer 3. Furthermore, the attenuation of spin waves in the magnetic layer 3 can be suppressed.

[0070] The metal layer 2 is a metal layer disposed between the piezoelectric layer 1 and the magnetic layer 3. The metal layer 2 functions as a buffer layer that suppresses the diffusion of elements between the piezoelectric layer 1 and the magnetic layer 3. Furthermore, the metal layer 2 serves as a base layer for forming the magnetic layer 3 on the piezoelectric layer 1.

[0071] The metal layer 2 is preferably single crystal. When the metal layer 2 is single crystal, the crystal order of the magnetic layer 3 formed on the metal layer 2 is improved. Furthermore, when the metal layer 2 is single crystal, the magnetic layer 3 can be grown as a single crystal. This allows vibrations to be efficiently propagated from the piezoelectric layer 1 to the magnetic layer 3 via the metal layer 2, efficiently generating spin waves in the magnetic layer 3. Furthermore, the attenuation of spin waves in the magnetic layer 3 can be suppressed.

[0072] By placing the metal layer 2 between the piezoelectric layer 1 and the magnetic layer 3, mutual element diffusion is suppressed between the piezoelectric layer 1 and the magnetic layer 3. Furthermore, by suppressing this diffusion, disturbance of the interface between the piezoelectric layer 1 and the magnetic layer 3 is suppressed.

[0073] Furthermore, by disposing the metal layer 2 on the piezoelectric layer 1 and forming the magnetic layer 3 on the metal layer 2, as described later, the crystal order of the magnetic layer 3 is improved. This allows vibrations to be efficiently propagated from the piezoelectric layer 1 to the magnetic layer 3 via the metal layer 2, efficiently generating spin waves in the magnetic layer 3. Furthermore, the attenuation of spin waves in the magnetic layer 3 can be suppressed.

[0074] Regarding the propagation of vibration to the magnetic layer 3 and the generation of spin waves in the magnetic layer 3 , high efficiency means that when the energy of the vibration is converted into spin waves, the ratio of the energy of the vibration converted into heat is small.

[0075] The metal layer 2 preferably comprises a layer of a metal having a cubic or hexagonal crystal system at room temperature, more preferably a layer of a metal having a body-centered cubic crystal system. The thickness of the metal layer is 3 nm or greater, and even more preferably 10 nm or greater. This can improve the crystal order of the magnetic layer 3, thereby increasing the efficiency of vibration propagation from the piezoelectric layer 1 to the magnetic layer 3, increasing the efficiency of spin wave generation in the magnetic layer 3, and suppressing spin wave attenuation in the magnetic layer 3. The metal layer 2 can be formed from a layer of a metal having a body-centered cubic crystal system at room temperature.

[0076] The metal layer 2 preferably has a thickness of 3 nm or greater, more preferably 10 nm or greater. The thickness of the metal layer 2 is preferably 40 nm or less. By making the metal layer 2 3 nm or greater, the crystal order of the magnetic layer 3 may be improved, thereby increasing the propagation efficiency of vibration from the piezoelectric layer 1 to the magnetic layer 3, increasing the efficiency of spin wave generation in the magnetic layer 3, and suppressing the attenuation of spin waves in the magnetic layer 3.

[0077] Furthermore, when the thickness of the metal layer 2 exceeds 40 nm, the vibration propagating from the piezoelectric layer 1 to the magnetic layer 3 may be attenuated, or the spin wave may be easily attenuated in the magnetic layer 3. A moderately thin metal layer 2 improves the efficiency of spin wave generation in the magnetic layer 3.

[0078] The metal layer contained in the metal layer 2 is preferably at least one metal selected from iron (Fe), chromium (Cr), and vanadium (V). This can improve the crystal order of the magnetic layer 3, thereby improving the propagation efficiency of vibration from the piezoelectric layer 1 to the magnetic layer 3, improving the efficiency of generating spin waves in the magnetic layer 3, and suppressing the attenuation of spin waves in the magnetic layer 3. The metal layer 2 can be formed by a layer of a metal that is a body-centered cubic crystal at room temperature. The metal layer 2 can be a layer of these metals. Iron (Fe), chromium (Cr), and vanadium (V) are metals that are a body-centered cubic crystal at room temperature and are preferred as metals forming the metal layer 2.

[0079] The metal layer 2 preferably has an average oxygen content of 5 at% or less. This suppresses disturbances at the interface between the metal layer 2 and the magnetic layer 3, allowing vibrations to efficiently propagate from the piezoelectric layer 1 to the magnetic layer 3 via the metal layer 2, effectively generating spin waves in the magnetic layer 3. Furthermore, the attenuation of spin waves in the magnetic layer 3 can be suppressed.

[0080] Magnetic layer 3 is formed from crystals of a Heusler alloy, a ferromagnetic material. In magnetic layer 3, vibrations generated in piezoelectric layer 1 are converted into spin waves. Furthermore, magnetic layer 3 functions as a medium for propagating the generated spin waves. The thickness of magnetic layer 3 is, for example, 5 nm to 100 nm.

[0081] The Heusler alloy forming the magnetic layer 3 can be represented by the chemical formula X2YZ. The crystal structure of this alloy is preferably an L21 structure. This allows for efficient conversion of vibrations from the piezoelectric layer 1 into spin waves. In the chemical formula X2YZ, X and Y are the same or different elements, and Z is an element different from X and Y.

[0082] In the Heusler alloy represented by the chemical formula X2YZ as described above, Y includes Y′ and Y″ (where Y″ is an element different from Y′), and the alloy can be represented by X2Y′. x Y″ 1-x In the Heusler alloy represented by the chemical formula X2YZ as described above, Z includes Z' and Z" (where Z" is an element different from Z'), and the alloy can be represented by X2YZ'. x In the following description, it can be expressed as X2Y′ x Y″ 1- x The alloy of Z is represented as X2(Y′,Y″)Z, which can be represented as X2YZ′ x Z″ 1-x The alloy is represented as X2Y(Z′,Z″).

[0083] An example of a preferred Heusler alloy for forming the magnetic layer 3 is an alloy represented by the chemical formula X2YZ, which has an L21 crystal structure and exhibits half-metallic properties (i.e., high spin polarization). Specific examples of such alloys include Co2FeSi, Co2FeAl, Co2Fe(Si,Al), Co2FeGa, Co2MnSi, Co2MnGe, Co2MnSn, Co2(Fe,Mn)Si, Co2MnGa, and Fe3Si. Furthermore, Fe3Si, when represented using the chemical formula X2YZ, is Fe2FeSi. When the Heusler alloy forming the magnetic layer 3 is one of these alloys, the propagation efficiency of spin waves in the magnetic layer 3 is improved, enabling long-distance propagation of spin waves. This high propagation efficiency of spin waves is particularly important when the stack 100 is used as the element 200.

[0084] The magnetization intensity of the magnetic layer 3 is 600emu / cm 3 The above is sufficient. This allows the vibration from the piezoelectric layer 1 to be efficiently converted into a spin wave. The magnetization intensity can be a value measured using a commercially available vibrating sample magnetometer. The magnetization intensity is a value at 25°C.

[0085] In addition, the damping constant of the magnetic layer 3 is (Magnetic friction coefficient)1.0×10 -2 Below, the damping constant is preferably 5.0×10 -3 The following is sufficient. This improves the propagation efficiency of the spin wave in the magnetic layer 3 and enables long-distance propagation of the spin wave. The damping constant can be calculated from the line width of the ferromagnetic resonance spectrum. This damping constant is a value at 25°C.

[0086] Ferromagnetic resonance (hereinafter also referred to as "FMR") refers to the following resonance phenomenon: when an AC magnetic field with an angular frequency ω is applied to a plane (xy plane) perpendicular to the direction of the effective magnetic field (set as the z-axis direction), the magnetization is subjected to the torque of the AC magnetic field and precesses about the z-axis at an angular frequency ω. When the frequency f of the AC magnetic field (=ω / 2π) matches the Larmor frequency of the magnetization, this precession is strongly excited.

[0087] The damping constant can be calculated as follows according to the disclosure of Non-Patent Document 4. The sample is placed on an antenna using a coplanar waveguide (hereinafter also referred to as "CPW"), and a vector network analyzer (hereinafter also referred to as "VNA") is used to scan the frequency of the microwave signal transmitted through the antenna while performing S 21 Parameter measurement. The resonance frequency f is obtained while changing the magnitude of the external static magnetic field H. res , FMR spectrum of half-peak width ΔH. The half-peak width ΔH is relative to the resonance frequency f res Plot the graph and calculate the damping constant from the slope.

[0088] The magnetic layer 3 is preferably single crystal. When the magnetic layer 3 is single crystal, the generation efficiency and transmission speed of spin waves in the magnetic layer 3 are significantly improved. The crystal order of the Heusler alloy used as the magnetic layer 3 affects the value of the damping constant, with a higher crystal order reducing the damping constant. Therefore, when the laminate 100 is used as the element 200, the performance of the element 200 can be improved, making this a preferred method.

[0089] In the laminate 100 , the diffusion of elements at the interfaces between the piezoelectric layer 1 , the metal layer 2 , and the magnetic layer 3 is 10 nm or less, preferably 5 nm or less, and the layers are preferably epitaxially bonded.

[0090] Furthermore, in the laminate 100, it is preferable to achieve matching of the acoustic impedances of the piezoelectric layer 1, the metal layer 2, and the magnetic layer 3. Matching the acoustic impedances of the layers means designing the laminate 100 so that the acoustic impedances of the layers are close to each other. By achieving matching of the acoustic impedances of the layers of the laminate 100, energy loss when vibrations (surface acoustic waves) generated in the piezoelectric layer 1 propagate to the magnetic layer 3 is reduced, thereby improving the efficiency of spin wave generation in the magnetic layer 3.

[0091] exist Figure 2 、 Figure 3 , an example of an element 200 including a laminate 100 is shown. Figure 2 It is a schematic diagram showing the stacked structure of the element 200 when viewed from the side surface (the electrode layer 64 side described later) of the layer of the stacked body 100 . Figure 3 This is a schematic diagram showing element 200 as viewed from above, from the magnetic layer 3 side of stack 100. In the following description, the side of stack 100 facing magnetic layer 3 is referred to as "upper," "upper side," or "upper surface side," and the opposite direction is referred to as "lower," "lower side," or "lower surface side." For example, in stack 100, magnetic layer 3 is positioned above metal layer 2, and piezoelectric layer 1 is positioned below magnetic layer 3. The stacking direction of the layers in stack 100 is the same as the vertical direction.

[0092] like Figure 2 As shown, the element 200 includes: a laminate 100 including a piezoelectric layer 1, a metal layer 2, and a magnetic layer 3; and an insulating layer 4 covering the metal layer 2 and the magnetic layer 3 and insulating them. Figure 3 As shown, the element 200 has electrode layers 61, 62, 63, and 64. In the element 200, the magnetic layer 3 and the insulating layer 4 are smaller than the piezoelectric layer 1 in a plan view and are arranged in the center of the plate surface of the piezoelectric layer 1. Figure 2 ) overlaps with the magnetic layer 3 in a plan view, and the metal layer 2 and the magnetic layer 3 have the same shape in a plan view. Figure 2 、 Figure 3 In FIG, the case where the magnetic layer 3 is rectangular is exemplified.

[0093] The insulating layer 4 is used to separate the metal layer 2 and the magnetic layer 3 from each other. Figure 3 The electrode layers 61, 62, 63, 64 and the outer insulating layer are shown. The insulating layer 4 can be a film formed of silicon dioxide (SiO2), for example.

[0094] The electrode layers 61 , 62 , 63 , and 64 are electrodes formed of a conductive metal such as gold.

[0095] The electrode layers 61, 63, and 64 are arranged on the piezoelectric layer 1. The electrode layer 61 is arranged close to the insulating layer 4 to such an extent that it does not contact the insulating layer 4. Figure 2 As shown, the electrode layer 62 is arranged on the upper surface portion of the insulating layer 4 on the upper surface side of the magnetic layer 3 .

[0096] The electrode layer 61 is an electrode (source) for applying a voltage (electric field) to the piezoelectric layer 1. The electrode layer 61 is disposed on the piezoelectric layer 1 and on the longitudinal end (first end) side of the rectangular magnetic layer 3. For example, a curtain-shaped (comb-shaped) electrode formed of a Ti / Au bilayer film can be used as the electrode layer 61.

[0097] The electrode layer 62 is an electrode (drain) for detecting a spin wave propagating through the magnetic layer 3. The electrode layer 62 is arranged at an end portion (second end portion) on the other side of the side where the electrode layer 61 is arranged.

[0098] By applying a voltage to the electrode layer 61, an electric field is applied to the piezoelectric layer 1. This generates surface acoustic waves in the piezoelectric layer 1 in the element 200. The surface acoustic waves generated in the piezoelectric layer 1 propagate from the piezoelectric layer 1 through the metal layer 2 to the magnetic layer 3. Furthermore, the surface acoustic waves generated in the piezoelectric layer 1 propagate through the stack 100 from the electrode layer 61 side along the longitudinal direction of the magnetic layer 3 toward the electrode layer 62 side. The propagation of these surface acoustic waves generates spin waves in the magnetic layer 3. The spin waves propagate through the magnetic layer 3 from the electrode layer 61 side along the longitudinal direction of the magnetic layer 3 toward the electrode layer 62 side. Spin waves that propagate through the magnetic layer 3 and reach the vicinity of the electrode layer 62 can be detected in the electrode layer 62 due to the induced electromotive force generated by the spin waves. In this embodiment, the magnetic layer 3 is formed of a Heusler alloy, effectively suppressing the attenuation of the spin waves propagating through the magnetic layer 3. Thus, in the element 200 , it is possible to achieve a reduction in heat generation, an increase in the degree of freedom in shape design, and an improvement in the reliability of signal transmission using spin waves.

[0099] Electrode layers 63 and 64 are a pair of electrodes (gates) located at one end (the third end) and the other end (the fourth end) in the width direction of the rectangular magnetic layer 3. By applying an electric field between these electrodes, the magnetism of the magnetic layer 3 is suppressed.

[0100] Specifically, by applying an electric field between electrode layers 63 and 64, spin waves propagating from electrode layer 61 to electrode layer 62 in magnetic layer 3 can be amplified or attenuated. In device 200, by switching between applying an electric field between electrode layers 63 and 64 (ON) and not applying it (OFF), the intensity of the spin waves detected in electrode layer 62 can be increased or decreased, allowing signals to be transmitted based on the intensity. Consequently, device 200 can function as a transistor. Thus, device 200 can function as a transistor without generating Joule heat due to current flow.

[0101] In addition, as described above, by switching the state of applying an electric field between the electrode layers 63 and 64 (ON) and the state of not applying the electric field (OFF), the intensity of the spin wave detected in the electrode layer 62 can be increased or decreased. This is because, for example, by switching the state of these electric fields, the damping constant of the magnetic layer 3 can be adjusted.

[0102] Furthermore, the laminate 100 can have a structure other than the structure of the element 200 described above. Furthermore, the laminate 100 is not limited to being used as a transistor-like element 200 described above, but can be used as other elements such as an amplifier element and a magnetic switch element. Furthermore, its use as a magnetic device other than these is not excluded.

[0103] The laminated body 100 and the element 200 including the laminated body 100 can be manufactured as follows.

[0104] As described above, the laminate 100 can be manufactured by a manufacturing method including the steps of forming the metal layer 2 on the piezoelectric layer 1 and forming the magnetic layer 3 on the metal layer 2 .

[0105] In the metal layer forming process, Figure 4 As shown, the metal layer 2 can be formed on the piezoelectric layer 1 that has been previously formed to a predetermined thickness by, for example, molecular beam epitaxy (MBE). Furthermore, the piezoelectric layer 1 can be a piezoelectric layer 1 with a smooth surface. Furthermore, the piezoelectric layer 1 is preferably a single-crystal piezoelectric layer 1. Furthermore, the metal layer 2 can be formed with a smooth surface. The surface of the piezoelectric layer 1 and the surface of the metal layer 2 each preferably have a root mean square surface roughness of 1 nm or less.

[0106] In the metal layer forming step, the metal layer 2 may be formed by molecular beam epitaxy at a growth temperature of 80° C. to 450° C. The growth temperature is preferably 200° C. to 400° C.

[0107] By setting the growth temperature in the metal layer formation step to the temperature described above, it is possible to suppress the diffusion of elements between the metal layer 2 and the piezoelectric layer 1. This can also suppress disturbances in the interface between the metal layer 2 and the piezoelectric layer 1. Furthermore, molecular beam epitaxy is suitable for forming the metal layer 2 at low temperatures, such as the growth temperature described above.

[0108] Furthermore, by setting the growth temperature in the metal layer formation step to the temperature described above, the growth of the metal layer 2 into an island shape can be suppressed, thereby suppressing deterioration in the surface flatness of the metal layer 2. By suppressing deterioration in the surface flatness of the metal layer 2, it is possible to prevent a decrease in the orderliness of the crystals of the magnetic layer 3 formed on the metal layer 2, thereby suppressing a decrease in the efficiency of spin wave generation in the magnetic layer 3 and suppressing attenuation of spin wave propagation in the magnetic layer 3 (for example, preventing an increase in the damping constant).

[0109] In addition, by setting the growth temperature in the metal layer forming process to the temperature described above, it is possible to prevent the piezoelectric layer 1 from deteriorating, that is, to prevent elements from diffusing from the piezoelectric layer 1 to the metal layer 2, or from diffusing from the metal layer 2 to the piezoelectric layer 1, thereby preventing the composition of the piezoelectric layer 1 from changing and deteriorating its characteristics as a piezoelectric body.

[0110] The magnetic layer forming step is performed after the metal layer forming step. In the magnetic layer forming step, the magnetic layer 3 is formed on the metal layer 2 by molecular beam epitaxy. Figure 1 The stack 100 is shown.

[0111] In the magnetic layer forming step, the magnetic layer 3 is formed at a growth temperature of 80°C to 450°C. This growth temperature is preferably 200°C to 400°C. In the magnetic layer forming step, a heat treatment to improve the crystal order of the magnetic layer 3 is permitted within a range where no disturbance occurs at the interfaces between the piezoelectric layer 1, the metal layer 2, and the magnetic layer 3.

[0112] Furthermore, during the magnetic layer formation process, even when the magnetic layer 3 is formed at a temperature lower than the growth temperature described above, the Heusler alloy can still be crystallized. However, when heat treatment is required to promote crystal ordering of the Heusler alloy in the magnetic layer 3 that has been temporarily crystallized at a low temperature (including crystallization to a B2 structure, crystallization to an unordered A2 structure, and polycrystallization), the effect of promoting crystal ordering may not be achieved unless the heat treatment is performed at a certain high temperature (e.g., a temperature exceeding 200°C). In such cases, forming the magnetic layer 3 at a growth temperature within the temperature range described above may facilitate the formation of a Heusler alloy layer with an L21 structure in the magnetic layer 3, compared to attempting heat treatment.

[0113] By setting the growth temperature in the magnetic layer formation step to the temperature described above, diffusion of elements between the metal layer 2 and the piezoelectric layer 1 can be suppressed. This can also suppress disturbances in the interface between the metal layer 2 and the piezoelectric layer 1. Furthermore, molecular beam epitaxy is suitable for forming the magnetic layer 3 at low temperatures, such as the growth temperature described above.

[0114] In addition, by setting the growth temperature in the magnetic layer forming process to the temperature described above, it is possible to prevent the piezoelectric layer 1 from deteriorating, that is, to prevent elements from diffusing from the piezoelectric layer 1 to the metal layer 2, or from diffusing from the metal layer 2 to the piezoelectric layer 1, thereby preventing the composition of the piezoelectric layer 1 from changing and deteriorating its characteristics as a piezoelectric body.

[0115] By setting the growth temperature in the magnetic layer forming step to the above-mentioned temperature, it is possible to suppress the diffusion of elements between the magnetic layer 3 and the metal layer 2. This can suppress the disorder of the interface between the magnetic layer 3 and the metal layer 2.

[0116] In addition, by setting the growth temperature in the magnetic layer forming process to the temperature described above, it is possible to prevent the deterioration of the magnetic layer 3, that is, to prevent elements from diffusing from the metal layer 2 to the magnetic layer 3, or from diffusing from the magnetic layer 3 to the metal layer 2, thereby preventing the composition of the magnetic layer 3 from changing and deteriorating its characteristics as a piezoelectric body.

[0117] When manufacturing the element 200 using the laminate 100, the laminate 100 is then patterned using a photolithography apparatus or the like. Figure 5 As shown, an etching process of removing a portion of the metal layer 2 and a portion of the magnetic layer 3 is performed using an etching device.

[0118] After removing a portion of the metal layer 2 and a portion of the magnetic layer 3 from the laminate 100, as shown in FIG. Figure 6 As shown, an insulating layer forming step is performed to form an insulating layer 4 made of silicon dioxide or the like on the surfaces of the remaining metal layer 2 and the magnetic layer 3 (surface portions that are exposed without forming an interface with other layers). The insulating layer 4 can be formed by patterning using a photolithography apparatus or the like and deposition (evaporation) using a vacuum thin film apparatus.

[0119] Finally, if Figure 2 、 Figure 3 As shown in FIG. 1 , electrode layers 61, 62, 63, and 64 are formed at predetermined positions as electrodes. These electrodes can be formed by patterning using a photolithography apparatus or the like and deposition (evaporation) using a vacuum thin film apparatus.

[0120] Example

[0121] Hereinafter, the laminated body of this embodiment will be further described based on examples.

[0122] (Example 1)

[0123] As described later, a chromium layer as a metal layer and a Co2FeSi layer as a magnetic layer were formed on a LiNbO3 substrate (Y-cut) as a piezoelectric layer to obtain a laminate of Example 1. Figure 7 , a TEM image of a cross section of the laminate of Example 1 is shown. In the following description, when referred to simply as a TEM image, it is a HAADF-STEM (High-Angle Annular Dark Field Scanning TEM) image taken at an accelerating voltage of 200 kV using a JEM-ARM200F manufactured by JEOL Ltd.

[0124] This laminate is produced by sequentially forming a metal layer and a ferromagnetic Heusler alloy layer as a magnetic layer on a LiNbO 3 substrate using molecular beam epitaxy (MBE) as follows.

[0125] As the LiNbO 3 substrate, a commercially available LiNbO 3 substrate (manufactured by YAMAJU CERAMICS CO., LTD., 128° Y-cut, 0.5 mm thick) was used.

[0126] First, the surface treatment of the LiNbO3 substrate is performed as follows. The LiNbO3 substrate is first chemically cleaned. During the chemical cleaning, dimethylacetamide is used to strip off the surface protective resist applied to the surface of the LiNbO3 substrate, and then the substrate surface is cleaned with isopropyl alcohol. While the LiNbO3 substrate is immersed in isopropyl alcohol, the substrate surface is wiped and polished with a cotton swab to perform cleaning with isopropyl alcohol. In addition, during the chemical cleaning, the surface of the substrate is gradually observed during the cleaning process with isopropyl alcohol to determine the end point of the cleaning. After blowing dry nitrogen to the substrate to dry it, the surface of the substrate is observed with an optical microscope. Repeat the cleaning with isopropyl alcohol, drying, and observation with an optical microscope until no particles on the substrate surface can be observed with an optical microscope. The state where no particles on the substrate surface can be observed with an optical microscope is regarded as the end point of the cleaning.

[0127] After the surface treatment of the LiNbO3 substrate, the LiNbO3 substrate is quickly mounted on a holder and transported to the input chamber of the MBE device. Then, after the substrate is moved to the growth chamber of the MBE device, the surface of the substrate is observed using a reflection high energy electron diffraction (RHEED) device mounted in the growth chamber to confirm that the desired diffraction pattern is observed. The substrate is then heat treated at 500°C for 60 minutes in the growth chamber. At this time, the vacuum degree in the MBE device is maintained at 1×10 -8 Torr or less.

[0128] After the heat treatment of the LiNbO 3 substrate, the substrate surface was observed using a RHEED device, and it was confirmed that a diffraction pattern was observed more clearly than before heating.

[0129] Next, a chromium layer, serving as a metal layer, was formed on the LiNbO3 substrate. While the LiNbO3 substrate was maintained at 200°C, chromium was heated and evaporated using a Knudsen cell and supplied to the substrate surface, forming the chromium layer on the LiNbO3 substrate. The chromium layer was formed while the substrate was rotated.

[0130] The growth rate of the chromium layer is to The chromium vapor deposition rate was adjusted using a crystal oscillating film thickness gauge installed in the MBE apparatus.

[0131] The thickness of the chromium layer was adjusted to 10 nm by the evaporation time. The vacuum degree of the MBE growth chamber was kept at 10 -9 The front half around Torr.

[0132] After the chromium layer was formed, the substrate surface was observed using a RHEED device, and a stripe-shaped diffraction pattern was observed, confirming that the chromium layer was formed as a single crystal.

[0133] Next, a Co2FeSi layer is formed on the chromium layer. While the temperature of the LiNbO3 substrate (hereinafter sometimes referred to as the laminated substrate) on which the chromium layer is formed is maintained at 200°C, the constituent elements (Co, Fe, and Si) of the Co2FeSi layer are heated and evaporated using a Knudsen cell and simultaneously supplied to the surface of the chromium layer of the laminated substrate, thereby forming the Co2FeSi layer on the chromium layer. The growth rate of the Co2FeSi layer is to Regarding the composition ratio of the Co2FeSi layer, the evaporation rate of each element was adjusted to a ratio corresponding to the composition ratio. In addition, the evaporation rate of each element was measured using a bare ionization meter mounted in the MBE device. The film thickness of the Co2FeSi layer was adjusted to 30nm by the evaporation time. The vacuum degree of the MBE growth chamber during the formation of the Co2FeSi layer was maintained at 10 -9 The front half around Torr.

[0134] After the Co2FeSi layer was formed, surface observation using a RHEED device confirmed a striped diffraction pattern. This indicates that the Co2FeSi layer was formed as a single crystal. Separately, high-resolution HAADF-STEM images of the Co2FeSi layer were taken to confirm that the crystals in the Co2FeSi layer had an L21 structure.

[0135] The laminated body of Example 1 was produced in the above-described manner.

[0136] observe Figure 7 As is apparent from the TEM image shown, in this laminate, diffusion of elements between the LiNbO 3 substrate, the chromium layer, and the Co 2 FeSi layer is suppressed, disorder at the interfaces between the layers is suppressed, and each interface is smooth.

[0137] The Co2FeSi layer of the laminate of Example 1 was subjected to FMR spectroscopy, and the damping constant (magnitude of magnetic friction) was evaluated based on the results. The damping constant was 3.3×10 -3 to 6.1×10 -3 That is, the magnetic friction of the Co 2 FeSi layer of the laminate of Example 1 was small, the attenuation of the spin wave was suppressed, and the laminate of Example 1 was evaluated to be suitable for use as a device such as a transistor.

[0138] In addition, in the present embodiment, the following apparatus and measurement conditions were employed for the measurement of the FMR spectrum.

[0139] The VNA used is Keysight E5071C.

[0140] As the probe, GGB Industries INC. picoprobe 40A-GSG-200-DS-NM was used.

[0141] The microwave intensity is 5dBm.

[0142] The measurement frequency is 1 to 20 GHz (scanning interval 19 MHz).

[0143] The external magnetic field strength is a maximum of 33000e.

[0144] The laminate of Example 1 was further subjected to surface analysis using EDX. Figure 8 , a TEM image of a region of the laminate of Example 1 subjected to surface analysis using EDX is shown. Figures 9 to 13 In the figure, the concentration distributions of Nb (L line), Cr (K line), Si (K line), Fe (K line), and Co (K line) obtained by surface analysis using EDX are shown in sequence. Figures 9 to 13 In the figure, the concentration of each element is represented by grayscale. The closer to black, the higher the concentration of the element to be detected.

[0145] according to Figures 8 to 13 As can be seen from the figures, in the laminate of Example 1, the diffusion of elements between the LiNbO 3 substrate, the chromium layer, and the Co 2 FeSi layer is suppressed.

[0146] The laminate of Example 1 was further subjected to line analysis using EDX. Figure 14 In the figure, regarding the cross section of the laminate of Example 1, the position and scanning direction for line analysis using EDX are superimposed on the TEM image. Figure 15 In FIG, a graph showing the relationship between the element concentration (at%) of C (K line), O (K line), Si (K line), Cr (K line), Fe (K line), Co (K line), and Nb (L line) obtained by line analysis using EDX and the scanning distance (nm) along the scanning direction is shown. In addition, the scanning direction and orientation are perpendicular to the layer structure of the stacked body. Figure 14 In the TEM image, the direction is from the Co2FeSi layer side to the LiNbO3 layer side. Figure 15 The distance 0 nm in the graph shown is the position of the surface of the Co2FeSi layer on the opposite side of the surface facing the chromium layer. Figure 15 In the graph shown, C (K line) is detected, but this is derived from the carbon film covering the cross section of the laminate during TEM observation, rather than being contained in the laminate.

[0147] Depend on Figure 15 As can be seen from the graph shown, in the laminate of Example 1, the diffusion of elements between the LiNbO 3 substrate, the chromium layer, and the Co 2 FeSi layer is suppressed.

[0148] In addition, according to Figure 15 The graph shown in FIG. 1 shows that if the average chromium content within a range of 10 nm from the interface of the chromium layer as the metal layer in the LiNbO3 substrate as the piezoelectric layer is 5 at% or less, then Figure 7 and Figure 14 As shown in the TEM image, the disorder of the interface between the LiNbO3 substrate and the chromium layer can be suppressed. Figure 15 The calculation basis of the above average chromium content obtained from the graph shown does not include the detected amount of carbon (C). The calculation of the above average chromium content is based on Figure 15 The graph shown shows values calculated based on the atomic composition of oxygen (O), silicon (Si), chromium (Cr), iron (Fe), cobalt (Co), and niobium (Nb).

[0149] In addition, according to Figure 15 The graph shown indicates that when the average oxygen content in the chromium layer as the metal layer is 5 at % or less, a state in which disorder at the interface between the chromium layer and the Co 2 FeSi layer is suppressed can be achieved.

[0150] (Comparative Example 1)

[0151] Next, unlike Example 1, a 30 nm thick vanadium layer was used as the metal layer instead of the 10 nm thick chromium layer. Furthermore, the growth temperature of the vanadium layer was set at 500°C. The remaining steps were the same as in Example 1, yielding a laminate of Comparative Example 1. In addition, surface observation using a RHEED device after the formation of the vanadium layer and the Co2FeSi layer in the laminate of Comparative Example 1 revealed clear striped diffraction patterns. This indicates that the Co2FeSi layer was formed as a single crystal.

[0152] exist Figure 16 , a TEM image of a cross section of the laminate of Comparative Example 1 is shown. Figure 16 The TEM images shown clearly show that in this laminate, the interfaces between the LiNbO3 substrate, the vanadium layer, and the Co2FeSi layer are disordered, and the unevenness of each interface is significantly larger than that of the laminate of Example 1. In addition, it is believed that the structural disorder caused by the infiltration of the inner side of the LiNbO3 substrate from the interface of the vanadium layer is caused by the significant diffusion of vanadium into the LiNbO3 substrate.

[0153] Furthermore, it is believed that the disturbance on the surface of the vanadium layer opposite the Co2FeSi layer or on the interface between the vanadium layer and the Co2FeSi layer is caused by the diffusion of oxygen from the LiNbO3 substrate into the vanadium layer. This is believed to have caused the disturbance on the surface of the vanadium layer opposite the Co2FeSi layer or on the interface between the vanadium layer and the Co2FeSi layer.

[0154] Ferromagnetic resonance spectroscopy was performed on the Co2FeSi layer of the laminate of Comparative Example 1, and the damping constant (magnetic friction) was evaluated based on the results. The damping constant was 1.4×10 -2 to 1.5×10 -2 That is, the Co 2 FeSi layer of the laminate of Comparative Example 1 has significantly greater magnetic friction than the Co 2 FeSi layer of the laminate of Example 1, and the spin wave is easily attenuated.

[0155] The laminate of Comparative Example 1 was further subjected to surface analysis using EDX. Figure 17 , a TEM image of a region subjected to surface analysis using EDX in the laminate of Comparative Example 1 is shown. Figures 18 to 22 In the figure, the concentration distributions of Nb (L line), V (K line), Si (K line), Fe (K line), and Co (K line) obtained by surface analysis using EDX are shown in sequence. Figures 18 to 22 In the figure, the concentration of each element is represented by grayscale. The closer to black, the higher the concentration of the element to be detected.

[0156] according to Figure 16 、 Figure 17As can be seen from the TEM image shown, in the laminate of Comparative Example 1, the interfaces between the LiNbO3 substrate, the vanadium layer, and the Co2FeSi layer are disordered. Figures 18 to 22 , a significant diffusion of vanadium from the vanadium layer to the LiNbO3 substrate was observed (ref. Figure 19 ).

[0157] The laminate of Comparative Example 1 was further subjected to line analysis using EDX. Figure 23 In FIG. 1 , the cross section of the laminate of Comparative Example 1 is shown with the position and scanning direction for line analysis using EDX superimposed on the TEM image. Figure 24 In FIG, a graph showing the relationship between the element concentration (at%) of C (K line), O (K line), Si (K line), V (K line), Fe (K line), Co (K line), and Nb (L line) obtained by line analysis using EDX and the scanning distance (nm) along the scanning direction is shown. In addition, the scanning direction and orientation are perpendicular to the layer structure of the stacked body. Figure 23 In the TEM image, the direction is from the Co2FeSi layer side to the LiNbO3 layer side. Figure 24 The distance 0 nm in the graph shown is the position of the surface of the Co2FeSi layer on the opposite side of the surface facing the chromium layer. Figure 24 In the graph shown, C (K line) is detected, but this is derived from the carbon film covering the cross section of the laminate during TEM observation, rather than being contained in the laminate.

[0158] Depend on Figure 24 As can be seen from the graph, in the laminate of Comparative Example 1, significant diffusion of elements occurs between the LiNbO3 substrate and the vanadium layer. Specifically, a large amount of vanadium diffuses from the vanadium layer in the LiNbO3 substrate. Furthermore, oxygen diffuses within the vanadium layer. It is believed that at least a portion of the oxygen diffused within the vanadium layer is supplied by the LiNbO3 substrate.

[0159] In addition, according to Figure 24 The graph shown in FIG. 1 shows that the average vanadium content within 10 nm of the interface with the vanadium layer as the metal layer in the LiNbO3 substrate as the magnetic layer is greater than 5 at%. Figure 16 As shown in the TEM image, the disorder of the interface between the LiNbO3 substrate and the vanadium layer is promoted. Figure 24 The calculation basis of the above average vanadium content obtained from the graph shown does not include the detected amount of carbon (C). The calculation of the above average vanadium content is based on Figure 24 The graph shown shows values calculated based on the atomic composition of oxygen (O), silicon (Si), vanadium (V), iron (Fe), cobalt (Co), and niobium (Nb).

[0160] In addition, according to Figure 24 The graph shown indicates that, in the vanadium layer as the metal layer, when the average oxygen content exceeds 5 at %, disorder is likely to occur at the interface between the vanadium layer and the Co 2 FeSi layer.

[0161] (Example 2)

[0162] Ferromagnetic resonance (FMR) has been used to demonstrate the ability to control the propagation of spin waves in a ferromagnetic Heusler alloy thin film (magnetic layer) in an electric field. This ability to control spin wave propagation was demonstrated by measuring whether the damping constant of the laminate (magnetic layer) can be controlled by the electric field strength, that is, by measuring the change in the damping constant with respect to the electric field strength.

[0163] As the element for this measurement, a Figure 25 Element 400 of the structure shown in FIG. Element 400 includes: an antenna substrate 300, with electrodes 71 and 72 formed on the surface of an oxide film 70a of a silicon substrate 7 comprising a silicon layer 70 and an oxide film 70a, which is a silicon oxide film, disposed on one surface of the silicon layer 70; a laminate 100 disposed on the antenna substrate 300; and an electrode 73 formed on the surface of the laminate 100 opposite to the antenna substrate 300. The laminate 100 is disposed so that the magnetic layer 3 faces the antenna substrate 300.

[0164] The laminate 100 used in this example was manufactured in the same manner as the laminate manufactured in Example 1. The piezoelectric layer 1 of the laminate 100 in this example was the same as the LiNbO3 substrate used in Example 1. Furthermore, the metal layer 2 was a 10 nm thick chromium layer, similar to Example 1. The magnetic layer 3 was a 30 nm thick Co2FeSi layer, similar to Example 1.

[0165] Electrodes 71, 72, and 73 include titanium layers 71a, 72a, and 73a, and gold layers 71b, 72b, and 73b. Titanium layers 71a and 72a are formed on the surface of oxide film 70a. Titanium layer 73a is formed on the surface of piezoelectric layer 1 of stacked body 100. Gold layers 71b, 72b, and 73b are formed on the surfaces of titanium layers 71a, 72a, and 73a, respectively. Electrodes 71 and 72 are arranged linearly and parallel to each other at a predetermined interval.

[0166] The CPW antenna 8 includes conductors 81, 82, and 83 arranged (wired) on the surface of the oxide film 70a in a manner that they are spaced apart and extend linearly and in parallel. The line width of the conductors 81, 82, and 83 is 100 μm, and the interval between adjacent lines is 50 μm. The CPW antenna 8 is arranged in parallel with the electrodes 71 and 72. The CPW antenna 8 is arranged between the electrodes 71 and 72, and is arranged at a predetermined distance from the electrodes 71 and 72. The two ends of the CPW antenna 8 are connected to the two ports of the VNA with probes. The VNA outputs microwaves while scanning the frequency to measure the transmission coefficient (S 21 parameter).

[0167] Conductors 81, 82, 83 include titanium layers 81a, 82a, 83a and gold layers 81b, 82b, 83b. Titanium layers 81a, 82a, 83a are formed on the surface of oxide film 70a. Gold layers 81b, 82b, 83b are formed on the surfaces of titanium layers 81a, 82a, 83a, respectively.

[0168] Electrodes 71, 72 and conductors 81, 82, and 83 were formed by depositing 5 nm of titanium on the surface of oxide film 70a using an electron beam evaporator to form titanium layers 71a, 72a, 81a, 82a, and 83a, followed by further depositing 300 nm of gold to form gold layers 71b, 72b, 81b, 82b, and 83b. Electrode 73 was formed by depositing 3 nm of titanium on the surface of piezoelectric layer 1 using an electron beam evaporator to form titanium layer 73a, followed by further depositing 100 nm of gold to form gold layer 73b.

[0169] An insulating layer 85 made of SiO2 is formed on the CPW antenna 8 (on the conductors 81, 82, and 83). The insulating layer 85 is formed by depositing SiO2 to a thickness of 50 nm using a sputtering device.

[0170] Conductive paste layers 75 and 76 and an insulating layer 85 are disposed between laminate 100 and antenna substrate 300. Conductive paste layers 75 and 76 are applied to electrodes 71 and 72, respectively, by coating or the like. Conductive paste layers 75 and 76 ensure electrical continuity between electrodes 71 and 72 of antenna substrate 300 and magnetic layer 3 of laminate 100, while also adhering and securing laminate 100 to antenna substrate 300. Insulating layer 85 protects CPW antenna 8 and insulates CPW antenna 8 from laminate 100.

[0171] The measurement of the change in damping constant with respect to electric field strength is performed as follows. While an external magnetic field is applied along the extension direction of the CPW type antenna 8, the voltage applied between the electrode 73 on the back side of the piezoelectric layer 3 and the electrode 71 of the antenna substrate 300 is changed, thereby changing the electric field strength acting on the stack 100, and the ferromagnetic resonance spectrum is measured via the CPW type antenna 8. Here, the electric field acting on the stack 100 is applied in the following direction, which is along the plate surface (in-plane direction) of the magnetic layer 3 and along a virtual surface including a direction orthogonal to the extension direction of the CPW type antenna 8 and a direction orthogonal to the plate surface of the magnetic layer 3. In addition, in this measurement, the electrode 71 and the electrode 72 are made to have the same potential. Then, the damping constant of the stack 100 is calculated from the line width of the ferromagnetic resonance spectrum. The graph of the damping constant calculated by this measurement with respect to the electric field strength is shown in FIG. Figure 26 As shown. Figure 26 In FIG. 1 , the electric field intensity is represented as electric field (kV / cm) on the horizontal axis and the damping constant (-) is represented on the vertical axis.

[0172] like Figure 26 As shown in Figure 2, the change in electric field strength (with or without applied electric field) is observed. Figure 25 The damping constant of the stack 100 of the element 400 shown changes. Specifically, it is observed that the damping constant of the stack 100 decreases when the electric field strength is increased. That is, in the element 400, the damping constant of the magnetic layer 3 can be adjusted by switching the state of the electric field via the electrodes 71 and 73. This result means that the degree of attenuation of the spin wave propagating in the epitaxial ferromagnetic Heusler alloy film (magnetic layer 3) can be controlled by the electric field acting thereon. In other words, it means that the basic operation of the magnon transistor is confirmed. As Figure 26 As shown, in this embodiment, an adjustment of the damping constant by about 30% can be observed at an electric field of 1 / 10 or less of the breakdown electric field (~100 kV / cm) of LiNbO 3 used as the piezoelectric layer 1 .

[0173] As described above, a laminated body, an element, and a method for manufacturing a laminated body can be provided.

[0174] [Other embodiments]

[0175] (1) In the above embodiment, the stacked body 100 is described as a stacked body in which the piezoelectric layer 1, the metal layer 2, and the magnetic layer 3 are stacked in this order. In addition, it is described that the stacked body 100 can be manufactured by a manufacturing method including the following steps: a metal layer forming step of forming the metal layer 2 on the piezoelectric layer 1; and a magnetic layer forming step of forming the magnetic layer on the metal layer 2. However, in the stacked body 100, the piezoelectric layer 1 before the metal layer 2 is formed does not need to be a separate layer (such as a substrate). For example, in the stacked body 100, the piezoelectric layer 1 may also be formed on another substrate, such as a silicon substrate.

[0176] (2) In the above embodiment, the example in which the electrode layers 63 and 64, serving as a pair of electrodes (gates), are arranged at one end (the third end) and the other end (the fourth end) in the width direction of the rectangular magnetic layer 3 is described. However, the arrangement of the gates is not limited to the above example. The arrangement of the gates can be appropriately modified depending on the structure and application of the element.

[0177] In addition, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited thereto, but can be appropriately modified within the scope not departing from the purpose of the present invention.

[0178] Industrial applicability

[0179] The present invention is applicable to a laminate, a device including the laminate, and a method for producing the laminate.

[0180] Description of Reference Numerals

[0181] 1: piezoelectric layer;

[0182] 100: laminate;

[0183] 2: Metal layer;

[0184] 200: component;

[0185] 3: magnetic layer;

[0186] 300: antenna substrate;

[0187] 4: Insulation layer;

[0188] 61: electrode layer;

[0189] 62: electrode layer;

[0190] 63: electrode layer;

[0191] 64: electrode layer;

[0192] 7: Silicon substrate;

[0193] 70: silicon layer;

[0194] 70a: oxide film;

[0195] 71: electrode;

[0196] 71a: titanium layer;

[0197] 71b: gold layer;

[0198] 72: electrode;

[0199] 72a: titanium layer;

[0200] 72b: gold layer;

[0201] 73: electrode;

[0202] 73a: titanium layer;

[0203] 73b: gold layer;

[0204] 75: conductive paste layer;

[0205] 76: conductive paste layer;

[0206] 8: CPW antenna;

[0207] 81: conductor;

[0208] 81a: titanium layer;

[0209] 81b: gold layer;

[0210] 82: conductor;

[0211] 82a: titanium layer;

[0212] 82b: gold layer;

[0213] 83: conductor;

[0214] 83a: titanium layer;

[0215] 83b: gold layer;

[0216] 85: Insulation layer.

Claims

1. A laminate comprising: a piezoelectric layer formed of a crystal of an oxide having piezoelectricity; a metal layer; and The magnetic layer is formed of crystals of a Heusler alloy which is a ferromagnetic material. The piezoelectric layer, the metal layer, and the magnetic layer are stacked in this order.

2. The laminate according to claim 1, wherein The magnetization intensity of the magnetic layer is 600emu / cm 3 above.

3. The laminate according to claim 1, wherein The damping constant of the magnetic layer is 1.0×10 -2 the following.

4. The laminate according to claim 1, wherein The damping constant of the magnetic layer is 5.0×10 -3 the following.

5. The laminate according to claim 1, wherein The Heusler alloy is Co2FeSi, Co2Fe(Si,Al), Co2MnSi, Co2(Fe,Mn)Si, Co2MnGa or Fe3Si. The laminate according to claim 1 , wherein: The Heusler alloy is Co2FeSi.

7. The laminate according to any one of claims 1 to 6, wherein The piezoelectric layer contains a compound represented by the chemical formula ABO3 as the oxide, A is a metal element, B is one or more metal elements different from A.

8. The laminate according to any one of claims 1 to 6, wherein The piezoelectric layer includes one or more selected from the group consisting of quartz crystal, lithium niobate, and lithium tantalate as the oxide.

9. The laminate according to any one of claims 1 to 6, wherein The oxide is lithium niobate.

10. The laminate according to any one of claims 1 to 6, wherein The metal layer includes a layer of a metal having a body-centered cubic crystal at room temperature and has a thickness of 3 nm or more.

11. The laminate according to any one of claims 1 to 6, wherein The oxide is lithium niobate, The metal layer is composed of a layer containing at least one metal selected from Fe, Cr, and V, and has a thickness of 10 nm or more.

12. The laminate according to claim 11, wherein The piezoelectric layer has an average content of the metal element constituting the metal layer within a range of 10 nm from the interface between the piezoelectric layer and the metal layer of 5 at % or less.

13. The laminate according to claim 11, wherein The average oxygen content of the metal layer is 5 at % or less.

14. A component comprising: a piezoelectric layer formed of a crystal of an oxide having piezoelectricity; a metal layer; and The magnetic layer is formed of crystals of a Heusler alloy which is a ferromagnetic material. The piezoelectric layer, the metal layer, and the magnetic layer are stacked in this order. The thickness of the metal layer is not less than 10 nm and not more than 40 nm, and the average oxygen content is not more than 5 at %, The piezoelectric layer has an average content of the metal element constituting the metal layer within a range of 10 nm from the interface between the piezoelectric layer and the metal layer of 5 at % or less.

15. The element according to claim 14, wherein The oxide is lithium niobate, The Heusler alloy is Co2FeSi.

16. A method for manufacturing a laminate, comprising: a metal layer forming step of forming a metal layer on the piezoelectric layer formed of a crystal of an oxide having piezoelectricity; as well as a magnetic layer forming step of forming a magnetic layer composed of crystals of a Heusler alloy which is a ferromagnetic material on the metal layer; In the magnetic layer forming step, the magnetic layer is formed by molecular beam epitaxy at a growth temperature of 80° C. or higher and 450° C. or lower.

17. The method for producing a laminate according to claim 16, wherein: The oxide is lithium niobate.

18. The method for producing a laminate according to claim 16 or 17, wherein: The Heusler alloy is Co2FeSi.

19. The method for producing a laminate according to claim 16 or 17, wherein: In the metal layer forming step, the metal layer is formed by molecular beam epitaxy at a growth temperature of 80° C. or higher and 450° C. or lower.

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